1. Field of the Invention
This invention relates to the removal of deposits comprising heavy hydrocarbonaceous materials and finely divided inorganic solids from wellbore surfaces and from other surfaces, such as the inside of piping such as tubing or casing and flowlines, using an alkyl polyglycoside surfactant composition.
2. Background of the Invention
Mixtures of oil, gas and water are frequently produced from oil fields. Processes for treating such mixtures to produce separate streams of oil, gas and water are well known. Typically the oil is separated and recovered as a product; the gas may be separated and recovered as a product; or, alternatively, the gas may be injected into a gas cap above an oil-bearing zone, into an oil-bearing zone or the like as recovered or as a miscible injectant which comprises the produced gas adjusted by the addition of nitrogen, carbon dioxide, hydrocarbons containing from one to about five carbon atoms and the like to adjust the specific gravity of the gas to produce a miscible injectant. The water may be recovered for injection or disposal by other means as known to those skilled in the art.
The separation is frequently accomplished in large settling tanks where the oil, gas and water are allowed to gravimetrically separate.
In many instances, the mixture of oil, gas and water is passed to central processing facilities for separation with the oil being recovered as a product and with the gas being either wholly or partially recovered as a product also. In some instances, the gas is distributed to injection wells and injected; and, in some fields, the water is similarly recovered, passed to injection wells and injected into the formation for the disposal of the water, for secondary oil recovery and the like.
It has been found, when such operations are conducted, especially when corrosion inhibitors are used in the lines leading from the wells to the central processing facility and the like, that, over a period of time, deposits of heavy hydrocarbonaceous materials and finely divided inorganic solids deposit on the inner surfaces of the lines. These deposits typically comprise finely-divided inorganic particles such as produced solids which may include hydraulic fracturing proppant, formation sand, formation fines and precipitates of materials such as iron sulfide. These particles become coated with corrosion inhibitor or other hydrocarbonaceous materials and subsequently accumulate additional quantities of heavy hydrocarbonaceous material in the flowlines, settling tank and the like. These deposits are referred to herein as "schmoo". The schmoo is a slimy, oily substance which adheres to almost any surface with which it comes in contact, and is difficultly removed from any surface and particularly from the inner surfaces of flowlines, water injection lines into the formation, wellbore surfaces and the like. The material is removable by pigging from flowlines which are of a sufficient size and configuration that pigs can be run through the lines. Such lines are routinely cleaned by pigging. Other lines, such as injection lines into wells, small diameter flowlines, the settling tank surfaces and formation surfaces are not accessible by pigging operations and, accordingly, the schmoo accumulates on the inner surfaces of these pipe lines, on the surfaces of the well and the like. The schmoo is detrimental to continued operations for a number of reasons. It has been found that it shelters bacteria which generate corrosive sulfides and other compounds beneath the schmoo and in contact with the pipe. This results in accelerated corrosion of the pipe surfaces, the formation of pits and eventual failure of the pipe. The replacement of pipe is expensive. The material can also accumulate to a thickness such that it flakes off the inner surfaces of the pipe and deposits in the lower portion of a well, the lower portion of a line or the like, and plugs the line or the formation in fluid communication with the pipe. This can result in the necessity for cleaning operations such as the use of coiled tubing with the injection of organic solvents such as mixtures of diesel oil and xylene, to clean such deposits from wellbores. Such deposits in wellbores are particularly common in wells which are used for alternating water and gas injection. In such wells, the schmoo dries on the inner surfaces of the tubing during gas injection and subsequently cracks and falls into the wellbore, thereby eventually plugging the wellbore, sometimes to a considerable depth. The removal of such deposits with coiled tubing units is expensive, time-consuming and does nothing to remove deposits from the surrounding formation.
In view of the difficulties created by the deposit of such materials, a continuing search has been directed to the development of a method for the removal of such deposits without the necessity for a pigging or coiled tubing operation for the removal of the deposits.